This invention relates to an optical switch for conducting and interrupting an optical path and an optical keyboard which utilizes the optical switch.
A measuring controller, a machine controller, and a monitor controller, etc. have mostly employed in general as signal control means an electric system signal device.
Such electric system signal devices have been feasibly affected by electromagnetic induction near a power plant, a substation or a power transmission line, as has been pointed out, and a spark generated from an electric contact sometimes causes a fire in environments where combustible gas exists.
To eliminate such defects, means for remotely controlling these devices have been provided, but in the case of remote control, the properness and the rapidness of the signal control are defective.
Further, in the case of the electric system signal devices, corrosion resistance is also defective due to the generation of static electricity at the signal input unit and the electric contacts made of emtal conductors.
To obviate such drawbacks it is desirable to construct a predetermined optical signal control system mainly with optical switches, and the optical signal control system can almost solve the above-mentioned drawbacks.
The general example of the optical switch applied to the optical signal control signal disclosed in Japanese Utility Model Publication No. 14014/1986 conducts and interrupts an optical path by attaching rod lenses to the ends of a pair of optical fibers for forming the optical path so that the ends are opposed in a housing and a light shielding plate is telescoped in or out between the rod lenses.
In the known example, since expensive components, such as the rod lenses have been employed, the optical switches become expensive.
In order only to reduce the cost, an optical switch of the structure that the end faces of the optical fibers are directly opposed without the rod lenses can be considered.
For example, optical fibers having large diameter cores are selectively used, and the coupling loss of the optical fibers in a light passing state can be reduced by decreasing the interval between the end faces of the optical fibers.
However, if the interval between the end faces of the optical fibers is reduced, as light shielding plate telescope in or out of the interval must be reduced in thickness. Thus, if the interval between the end faces of the optical fibers and the light shielding plate are not accurately formed correspondingly, the end faces of the optical fibers are damaged due to the contact of the end faces of the optical fibers and the light shielding plate to cause a foreign material to be bonded thereto so that the manufacture of the optical fiber become difficult.
Particularly, the damage and the adherence of a foreign material to the end faces of the optical fibers have become large problems in plastic optical fibers.
When the interval between the end faces of the optical fibers is reduced and the thickness of the light shielding plate is reduced in order to reduce the coupling loss between the optical fibers or to simplify the optical switch, an optical signal is passed through the thin light shielding plate with the result that the interruption of the optical path become incomplete.
In other devices, the optical switch must be reduced as small as possible to be associated therein, and it is very important that the assembling structure is stable and the attachment to a keyboard is facilitated.